Java Tutorial/Log/Log Formatter

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Create custom formatter

import java.util.logging.ConsoleHandler;
import java.util.logging.Formatter;
import java.util.logging.Handler;
import java.util.logging.LogRecord;
import java.util.logging.Logger;
public class MainClass {
  private static Logger logger = Logger.getLogger("SimpleFormatterExample");
  private static void logMessages() {
    logger.info("Line One");
    logger.info("Line Two");
  }
  public static void main(String[] args) {
    logger.setUseParentHandlers(false);
    Handler conHdlr = new ConsoleHandler();
    conHdlr.setFormatter(new Formatter() {
      public String format(LogRecord record) {
        return record.getLevel() + "  :  " + record.getSourceClassName() + " -:- "
            + record.getSourceMethodName() + " -:- " + record.getMessage() + "\n";
      }
    });
    logger.addHandler(conHdlr);
    logMessages();
  }
}





Creating a Custom Formatter for a Logger Handler

import java.util.Date;
import java.util.logging.FileHandler;
import java.util.logging.Formatter;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import java.util.logging.Logger;
class MyHtmlFormatter extends Formatter {
  public String format(LogRecord rec) {
    StringBuffer buf = new StringBuffer(1000);
    if (rec.getLevel().intValue() >= Level.WARNING.intValue()) {
      buf.append("<b>");
      buf.append(rec.getLevel());
      buf.append("</b>");
    } else {
      buf.append(rec.getLevel());
    }
    buf.append(" ");
    buf.append(rec.getMillis());
    buf.append(" ");
    buf.append(formatMessage(rec));
    buf.append("\n");
    return buf.toString();
  }
  public String getHead(Handler h) {
    return "<HTML><HEAD>" + (new Date()) + "</HEAD><BODY><PRE>\n";
  }
  public String getTail(Handler h) {
    return "</PRE></BODY></HTML>\n";
  }
}
public class Main {
  public static void main(String[] argv) throws Exception {
    Logger logger = Logger.getLogger("com.mycompany");
    FileHandler fh = new FileHandler("mylog.html");
    fh.setFormatter(new MyHtmlFormatter());
    logger.addHandler(fh);
    logger.setLevel(Level.ALL);
    logger.severe("my severe message");
    logger.info("my info message");
    logger.entering("Main class", "myMethod", new Object[] { "para1", "para2" });
  }
}





Define your own Custom Formatter

import java.util.logging.Formatter;
import java.util.logging.LogRecord;
public class CustomFormatter extends Formatter {
  public synchronized String format(LogRecord record) {
    String methodName = record.getSourceMethodName();
    String message = record.getMessage();
    StringBuffer buffer = new StringBuffer(50);
    buffer.append(methodName);
    buffer.append("=");
    buffer.append(message);
    return buffer.toString();
  }
}





Logger with XMLFormatter and FileHandler

import java.util.logging.FileHandler;
import java.util.logging.Handler;
import java.util.logging.Logger;
import java.util.logging.XMLFormatter;
public class Main {
  public static void main(String[] args) throws Exception {
    Logger logger = Logger.getLogger("my.log");
    Handler handler = null;
    handler = new FileHandler("messages.log");
    logger.addHandler(handler);
    handler.setFormatter(new XMLFormatter());
    logger.info("Our first logging message");
    logger.severe("Something terrible happened");
  }
}





Log HTML formatter

import java.util.Date;
import java.util.logging.FileHandler;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogManager;
import java.util.logging.LogRecord;
import java.util.logging.Logger;
import java.util.logging.XMLFormatter;
class HTMLFormatter extends java.util.logging.Formatter {
  public String format(LogRecord record) {
    return ("<tr><td>" + (new Date(record.getMillis())).toString() + "</td><td>"
        + record.getMessage() + "</td></tr>\n");
  }
  public String getHead(Handler h) {
    return ("<html>\n  <body>\n" + "<Table border>\n<tr><td>Time</td><td>Log Message</td></tr>\n");
  }
  public String getTail(Handler h) {
    return ("</table>\n</body>\n</html>");
  }
}
public class LoggingHTMLFormatter {
  public static void main(String args[]) throws Exception {
      LogManager lm = LogManager.getLogManager();
      Logger parentLogger, childLogger;
      FileHandler xml_handler = new FileHandler("log_output.xml");
      FileHandler html_handler = new FileHandler("log_output.html");
      parentLogger = Logger.getLogger("ParentLogger");
      childLogger = Logger.getLogger("ParentLogger.ChildLogger");
      lm.addLogger(parentLogger);
      lm.addLogger(childLogger);
      parentLogger.setLevel(Level.WARNING);
      childLogger.setLevel(Level.ALL);
      xml_handler.setFormatter(new XMLFormatter());
      html_handler.setFormatter(new HTMLFormatter());
      parentLogger.addHandler(xml_handler);
      childLogger.addHandler(html_handler);
      childLogger.log(Level.FINE, "This is a fine log message");
      childLogger.log(Level.SEVERE, "This is a severe log message");
      xml_handler.close();
      html_handler.close();
  }
}





Set log Formatter

import java.util.logging.FileHandler;
import java.util.logging.Logger;
import java.util.logging.SimpleFormatter;
public class MainClass {
  private static Logger logger = Logger.getLogger("LogToFile2");
  public static void main(String[] args) throws Exception {
    FileHandler logFile = new FileHandler("LogToFile2.txt");
    logFile.setFormatter(new SimpleFormatter());
    logger.addHandler(logFile);
    logger.info("A message logged to the file");
  }
}





Setting the Formatter of a Logger Handler

import java.util.logging.FileHandler;
import java.util.logging.Logger;
import java.util.logging.SimpleFormatter;
public class Main{
  public static void main(String[] argv) throws Exception{
    Logger logger = Logger.getLogger("com.mycompany");
    FileHandler fh = new FileHandler("mylog.txt");
    fh.setFormatter(new SimpleFormatter());
    logger.addHandler(fh);
    // fh = new FileHandler("mylog.xml");
    // fh.setFormatter(new XMLFormatter());
    // logger.addHandler(fh);
    // Log a few messages
    logger.severe("my severe message");
    logger.warning("my warning message");
    logger.info("my info message");
    logger.config("my config message");
    logger.fine("my fine message");
    logger.finer("my finer message");
    logger.finest("my finest message");
  }
}





XMLFormatter based Logging

import java.util.logging.FileHandler;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import java.util.logging.XMLFormatter;
public class Main {
  public static void main(String args[]) throws Exception{
    XMLFormatter formatter = new XMLFormatter();
    LogRecord record = new LogRecord(Level.INFO, "XML message..");
    FileHandler handler = new FileHandler("newxml.xml");
    handler.setFormatter(formatter);
    handler.publish(record);
    handler.flush();
  }
}


Источник — «http://jexp.ru/index.php?title=Java_Tutorial/Log/Log_Formatter&oldid=4274»